Doing a masters before a Bsc

So I’ve completed a BSc in biology and geography and I’ve applied and been given an offer to study biomedical science at NTU.
Now I want to become a biomedical scientist but that obviously requires a BSc in biomedical science, which I don’t have.

My question is, can I do a biomed MSc, and then AFTER do a second Bsc in biomed??
I currently work at the NHS and I know they do degree apprenticeships, but I need to get a promotion to do this.

Should I do the MSc anyway?? And when I get the promotion at work, then do the BSc degree apprenticeship?

I think you need to stop thinking about different qualifications and start by focusing on what it is you actually want to do as a job. You say you want to become a biomedical scientist in the NHS - do you mean a BMS, or do you mean a clinical scientist? These are different job roles with different requirements.
If you want to become a clinical scientist, you would need to go through the NHS STP. It doesn't matter how many previous degrees you've gotten, this is the singular route to becoming a clinical scientist. As I understand, normally you would earn a masters degree in the process of the STP. Also I believe most tracks just require a bioscience degree in general. Therefore, if your goal is to become a clinical scientist, I don't see any merit in doing any extra degrees and you should just apply directly to the scheme.
If you want to become a BMS, you will need an IBMS accredited undergraduate degree and registration with the HCPC. Registration with the HCPC requires you have completed a professional portfolio in an approved NHS pathology laboratory. Most of the healthcare science (life sciences) degrees that include integrated placements to complete this portfolio no longer are accepting applicants, as they have mainly transitioned to apprenticeship schemes for existing NHS staff. If you don't complete an apprenticeship then you'd need to do an entire IBMS accredited undergraduate degree, then competitively apply to placements (where there are 100s of applicants for each, and most placements they prioritise existing staff on apprenticeships for), and either hope you get one, or complete the degree then work as a Band 2/3 MLA for several years and hope your manager permits you to work on the professional portfolio as part of your job.
Given that in either route a standalone masters degree does not factor in as a requirement, you can rule out that possibility as a waste of time and money for achieving your goals. In terms of achieving your goals the most straightofrward and direct options would be either to apply to the STP (for clinical scientist careers) or to apply to an apprenticeship to become a BMS (for BMS careers). Doing an IBMS accredited degree without guaranteed placements is the worst possible option because then you need to (self fund, unless part-time) a whole new undergraduate degree, with no guarantee you will get a placement or a job that would allow you to complete the professional portfolio to ultimately become a BMS (and you may end up having to go through the apprenticeship route in the end anyway).
Therefore, I don't think it's worthwhile pursuing any of those degrees. I think you should apply to the STP or apply to a BMS apprenticeship scheme as applicable. No other option provides any remote guarantee of eventually achieving your goals and they all take much more time and money.

I unfortunately cannot apply for the bms apprenticeship scheme at the moment because my current nhs lab job doesn’t allow it. Due to it not being scientific enough to be able to support in the apprenticeship scheme.

I guess what I was trying to say was can I do a MSc in biomed/any other subject area I’m interested in, and THEN when I get my promotion to an AP where the bms apprentice scheme is an option, do that.

So I’ve completed a BSc in biology and geography and I’ve applied and been given an offer to study biomedical science at NTU.
Now I want to become a biomedical scientist but that obviously requires a BSc in biomedical science, which I don’t have.
My question is, can I do a biomed MSc, and then AFTER do a second Bsc in biomed??
I currently work at the NHS and I know they do degree apprenticeships, but I need to get a promotion to do this.
Should I do the MSc anyway?? And when I get the promotion at work, then do the BSc degree apprenticeship?